In recent years, energy harvesting has attracted much attention. In [1]}, resource allocation and fairness have been investigated to maximize sum-throughput. As an extension of [1]}, the authors in [3]} studied a wireless powered communication network (WPCN) with a full-duplex hybrid access point (HAP) that enables the HAP to broadcast energy and receive independent information from the users simultaneously. Energy harvesting CRNs (EH-CRNs) have been introduced for many sensor network applications. For applications with higher energy consumption, WPCN can be combined with a CRN to form cognitive-WPCN (CWPCN). In [4]}, authors studied the sum-throughput maximization problem for a CWPCN, in which SUs utilize an existing licensed spectrum for energy harvesting and data transmission. A multi-user MIMO CWPCN is studied in [5]}, wherein the optimal time allocation and transmit covariance matrices have been provided to maximize the network sum-throughput. A new frame structure has been suggested in [6]}. The authors split the time frame into four slots for spectrum sensing and data transmission, each with a separate energy harvesting time slot. Then they obtained power outage probability. In [7]}, the authors integrated an energy harvesting network with a cooperative CRN. They proposed a novel scheme and investigated resource allocation and fairness problems. Authors in [8]} studied the sum-throughput maximization problem in a WPCN, wherein users transmit to the HAP in a dual-hop manner. An underlay multi-hop EH-CRN has been investigated in [9]}. The authors studied the end-to-end throughput maximization problem and calculated time and power allocations thanks to the convex optimization techniques.
